1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device. More particularly, the present invention relates to a liquid crystal display (LCD) device module having two main viewing angles and a method of driving the liquid crystal display (LCD) device.
2. Discussion of the Related Art
In general, a liquid crystal display (LCD) device includes two substrates facing and spaced apart from each other and a liquid crystal layer interposed between the two substrates. Liquid crystal molecules in the liquid crystal layer have optical anisotropy and polarizability, and are aligned with directional characteristics resulting from their long, thin shapes. The alignment direction of the liquid crystal molecules can be controlled by applying an electric field thereto. Accordingly, a desired image can be obtained by refracting and transmitting incident light and controlling the electric field applied to a group of liquid crystal molecules within particular pixel regions. In addition, active matrix liquid crystal display (AMLCD) devices, where thin film transistors (TFTs) and pixel electrodes connected to the TFTs are arranged in a matrix, have been widely used because of their high resolution and superiority in displaying moving images.
FIG. 1 is an exploded perspective view of a liquid crystal display device according to the related art. In FIG. 1, a liquid crystal display (LCD) device includes first and second substrates 110 and 120, and a liquid crystal layer 130 therebetween. A gate line “GL” and a data line “DL” are formed on an inner surface of the first substrate 110. The gate line “GL” and the data line “DL” cross each other to define a pixel region “PA.” A thin film transistor (TFT) “T” is connected to the gate line “GL” and the data line “DL.” In addition, a pixel electrode 112 connected to the TFT “T” is formed in the pixel region “PA.” A black matrix 124 is formed in an inner surface of the second substrate 120. A color filter layer 126 including red, green and blue color filters 126a, 126b and 126c is formed on the black matrix 124 and a common electrode 122 is formed on the color filter layer 126. The pixel electrode 112 and the common electrode 122 are formed of a transparent conductive material such as an indium-tin-oxide (ITO) and indium-zinc-oxide (IZO). When the TFT “T” is turned on, the liquid crystal layer 130 between the pixel electrode 112 and the common electrode 122 is rearranged according to an image signal applied to the pixel electrode 112 and light transmittance is adjusted according to the rearrangement of the liquid crystal layer 130. As a result, a required image is displayed.
In the LCD device of FIG. 1, since the liquid crystal layer 130 is driven by a vertical electric field generated between the pixel electrode 112 and the common electrode 122, the LCD device has high transmittance and high aperture ratio. However, when a voltage is applied to a liquid crystal layer 130 having a horizontal arrangement where liquid crystal molecules in upper and lower portions are twisted by 90°, the liquid crystal molecules are rearranged to have a polarization value of 90°. As a result, contrast ratio and brightness vary extremely according to a viewing angle and a wide viewing angle is seldom obtained.
To solve the above problems, various LCD devices such as an in-plane switching (IPS) mode LCD device, a fringe field switching (FFS) mode LCD device and a vertical alignment (VA) mode LCD device are suggested. In the IPS mode LCD device, the liquid crystal layer is adjusted using a horizontal electric field. The FFS mode LCD device is suggested for improving aperture ratio and transmittance of the IPS mode LCD device. In the VA mode LCD device, the ordinary axis of the liquid crystal molecule is aligned along a direction perpendicular to substrates.
FIGS. 2A to 2C are cross-sectional views showing an IPS mode LCD device, an FFS mode LCD device and a VA mode LCD device, respectively, according to the related art. As shown in FIG. 2A, an IPS mode LCD device includes a first substrate 210, a second substrate 220 and a liquid crystal layer 230 between the first and second substrates 210 and 220. A pixel electrode 212 and a common electrode 222 are formed on the first substrates 210, and liquid crystal molecules in the liquid crystal layer 230 are arranged along a horizontal electric field 200 between the pixel electrode 212 and the common electrode 222. Since variation in refractive index according to a viewing angle is relatively small, a viewing angle is improved. However, aperture ratio and brightness are reduced. To improve the disadvantages of an IPS mode LCD device, the FFS mode LCD device is suggested.
In FIG. 2B, an FFS mode LCD device includes a first substrate 210, a second substrate 220 and a liquid crystal layer 230 between the first and second substrates 210 and 220. A common electrode 222 having a plate shape is formed in a pixel region on the first substrate 210. An insulating layer 214 is formed on the common electrode 222, and a plurality of pixel electrodes 212 are formed on the insulating layer 214. The plurality of pixel electrodes 212 are parallel to and spaced apart from each other. Since a horizontal electric field is generated in a gap having several angstroms (Å) between the common electrode 222 and the pixel electrode 212, the horizontal electric field has a strong intensity. In addition, since liquid crystal molecules over the common electrode 222 are arranged along the horizontal electric field, aperture ratio and brightness are improved. When the common electrode 222 is formed to have a bar shape, the common electrode 222 is disposed very close to the pixel electrode 212
In FIG. 2C, a VA mode LCD device includes a first substrate 210, a second substrate 220 and a liquid crystal layer 230 between the first and second substrates 210 and 220. A pixel electrode 212 is formed on the first substrate 210, and a common electrode 222 is formed on the second substrate 220. Liquid crystal molecules in the liquid crystal layer 230 are vertically aligned. In addition, a pixel region is divided into domains having main viewing angles different from each other. This multi-domain structure is obtained by a slit or a protrusion in the common electrode 222. Since a vertical electric field is distorted due to the slit or the protrusion, the VA mode LCD device has a multi-domain structure.
Since an IPS mode LCD device, an FFS mode LCD device and a VA mode LCD device have a wide viewing angle, an identical image having a high display quality are displayed to users along various viewing angles. When the users along various viewing angles want to watch different images, a plurality of LCD devices are required. For example, when an LCD device is disposed at a central portion of a car, a driver may look forward to watching an image regarding a car navigation system (CNS) and a passenger may look forward to watching an image regarding a movie or a broadcast. However, a plurality of LCD devices cause increase in space and cost.